Systematically tuning the spatial environment around the active sites of synthetic catalysts is a difficult challenge. Here, we show how this can be accomplished in the pores of multicomponent ...metal–organic frameworks. This relies on embedding a catalytic unit in a pore of the MUF-77 framework and then tuning its environment by introducing different functional groups to the surrounding linkers. This approach benefits from the structural regularity of MUF-77, which places each component in a precise location to circumvent disorder. Prolinyl groups, which are catalytically competent toward asymmetric aldol reactions, were selected as the catalytic unit. Since every prolinyl group is positioned in an identical environment, correlations between the pore architecture and the activity of these single-site catalysts can be elucidated. Systematic engineering of the pore structure, which is achieved by installing modulator groups on the framework linkers, impacts on the reaction rate and the enantiomeric excess of the aldol products. Furthermore, the spatial environment around the proline catalyst can override its innate stereochemical preference to dictate the preferred enantiomer of the reaction product. These results offer a new way to design three-dimensional active site environments for synthetic catalysts.
Grouped and right‐censored (GRC) counts are widely used in criminology, demography, epidemiology, marketing, sociology, psychology and other related disciplines to study behavioural and event ...frequencies, especially when sensitive research topics or individuals with possibly lower cognitive capacities are at stake. Yet, the co‐existence of grouping and right‐censoring poses major difficulties in regression analysis. To implement generalised linear regression of GRC counts, we derive modified Poisson estimators and their asymptotic properties, develop a hybrid line search algorithm for parameter inference, demonstrate the finite‐sample performance of these estimators via simulation, and evaluate its empirical applicability based on survey data of drug use in America. This method has a clear methodological advantage over the ordered logistic model for analysing GRC counts.
In this paper, a (2+1)-dimensional generalized Konopelchenko-Dubrovsky-Kaup-Kupershmidt system in fluid mechanics and plasma physics is investigated. Bilinear form under certain coefficient ...constraints is given via the Hirota method. The
N
th-order Pfaffian solutions are proved by means of the Pfaffian technique, where
N
is a positive integer.
N
-soliton and the higher-order breather solutions are exported through the
N
th-order Pfaffian solutions. Different two-soliton/breather structures and their dynamics are derived. Elastic/inelastic interactions between the two solitons/breathers are investigated. Graphical representations of the influence of the coefficients in the equation on the velocities and amplitudes of the solitons and breathers are exhibited.
Aim
Climate change is expected to have important effects on plant phenology and carbon storage, with further shifts predicted in the future. Therefore, we proposed the community carbon accumulation ...rate (CAR) from the start of the growing season (SOS) to the peak of the growing season (POS) to fill the gap that the dynamic interactions between plant phenology and plant carbon research.
Location
Tibetan Plateau.
Major taxa
Alpine grassland plants.
Time period
2015.
Methods
We conducted a transect survey across grasslands to measure community aboveground net primary production and carbon concentration. Additionally, phenology indicator data (SOS and POS) were extracted from the Global Inventory Modeling and Mapping Studies (GIMMS) normalized difference vegetation index version 3 database. Next, we used ‘changepoint’ analysis to detect the patterns of CARs, and performed linear regression and one‐way ANOVA to explore the variability of CARs in response to the environmental factors. Ultimately, the total effects of environmental factors on CARs were illustrated by a structural equation model.
Results
Our results indicated that three CAR patterns were detected, which are low‐CAR (0.15 g/m2/day), medium‐CAR (0.31 g/m2/day) and high‐CAR (0.84 g/m2/day) patterns. We found that the availabilities of water and heat mediated CARs by regulating soil nutrition variability, and that drought climate and insufficient soil resources co‐constrained the community CAR at long time‐scales. In contrast, high CAR could be explained by more water and heat availability via either direct or indirect effects on soil moisture and soil nutrients.
Main conclusions
Our findings highlight that water and heat availability are critical driving factors in ecological carbon accumulation processes undergoing climate change. Meanwhile, the vegetative phenology also has important effect on carbon accumulation. Consequently, we propose incorporating the dynamic interactions between plant phenology and plant carbon into the ecological carbon cycle model to improve our understanding of resource utilization and survival strategies of plants under environmental change.
Abstract
Converting mechanical energy into photon emission provides a promising route for intelligent sensing, self‐powered lighting, and distributed energy harvesting, which is of great significance ...for finding a feasible solution to the current sensing technical bottleneck and energy crisis. As the basis for understanding the conversion mechanism and realizing high‐frequency mechanical energy utilization, elucidating the dynamic process of intensity variation in the mechano‐to‐photon conversion remains a great challenge. Herein, a time‐domain characterization scheme that enables to unravel the intrinsic decay of mechanoluminescence (ML) with lifetimes from milliseconds down to tens of microseconds is constructed. It is demonstrated that ML decay characterization is an important tool to reveal the dynamics of charge migration in ML materials. The ML decay in a typical self‐reproducible ML material ZnS:Mn
2+
shows temperature dependence and stress fluctuation resistance, which opens up a new reliable approach for self‐powered and remote temperature sensing. Finally, benefiting from the shortest ML lifetime recorded to date, an ultrafast‐response stress sensor that enables to detect individual pulses of ultrasonic waves with ML sensing technology is developed.
Metal–organic frameworks (MOFs) exhibit a broad range of luminescence characteristics due to the vast array of metal ions and organic linkers available as building blocks. Systematic control over the ...emissive output of MOFs is highly sought after. Methods for tuning emission profiles are emerging based largely on luminescent metal ions and the encapsulation of emissive guests. Herein, we show how the functionalization of the organic linkers of a series of multicomponent MUF-77 (MUF = Massey University Framework) materials can methodically tune their spectral output. This was quantified by chromaticity diagrams. White-light emission was obtained by combining the photophysical characteristics of the three distinct organic fluorophores present in these materials. Our results also show that both (i) energy transfer interactions between the organic components and (ii) noncovalent interactions with guests can also be harnessed to tune the emission. These results establish multicomponent metal–organic frameworks as fluorescent materials with unique spectral characteristics.
•Heat transfer enhancement based on multi-longitudinal vortices is reviewed.•Heat transfer optimization gives the optimal flow fields for heat transfer.•Generating multi-longitudinal vortices results ...in heat transfer enhancement.•Research gaps and future research directions are provided.
In this work, a review on single-phase convective heat transfer enhancement based on multi-longitudinal vortices is carried out. Theoretical investigations on convective heat transfer optimization from different principles such as entropy generation minimization principle, field synergy principle, entransy dissipation extremum principle, power consumption minimization principle, and exergy destruction minimization principle for the better trade-off between heat transfer augmentation and flow resistance reduction are firstly evaluated. It is found that the optimal flow fields are mainly characterized by multi-longitudinal vortices, implying that heat transfer enhancement techniques which can generate the flow patterns similar to the optimal flow fields may also enjoy the satisfactory balance between heat transfer enhancement and flow resistance reduction. Then, various techniques such as artificial roughness, special-shaped tubes, multiple swirl devices, and longitudinal vortex generators that can construct the flow pattern of multi-longitudinal vortices are summarized. Results indicate that most of the techniques show excellent thermal-hydraulic performance, but some techniques still suffer from high flow resistance. Based on the discussion, some new perspectives on the existing research gaps, challenging, and future research directions have been provided for the development of enhanced heat transfer techniques by generating multi-longitudinal vortices in heat exchanger tubes.
Epidermolysis bullosa pruriginosa (EBP) is a rare variant of dystrophic epidermolysis bullosa caused by COL7A1 gene mutation. Intense pruritus and nodular prurigo‐like lesions are the main features ...of the disease. To date, the treatment strategies for this condition are not well established. Recent studies have indicated that type 2 inflammation plays a role in the pathophysiology of EBP, suggesting Th2 cytokines could be potential therapeutic targets. In this prospective case series study, we reported three patients with EBP, diagnosed by clinical manifestations, histopathological evaluations, and genetic sequencing, two of whom were treated with dupilumab for 20 weeks. Results showed that the clinical symptoms, pruritus, and quality of life of the patients were significantly improved, as measured by the Epidermolysis Bullosa Disease Activity and Scarring Index, the Visual Analog Scale, and the Children's Dermatology Life Quality Index. Serum immunoglobulin E levels also fell gradually over the 20‐week treatment period. Immunotyping of Th1/2/17 cell subsets in peripheral blood by flow cytometry revealed a higher Th2 but parallel Th1 and Th17 cell subsets in patients compared to healthy controls, and a significant decrease in Th2 and an increase in Th17 cells after dupilumab administration. Of note, after 20 weeks of dupilumab treatment, the expression of type VII collagen in the basement membrane of the skin lesion of the patients significantly increased, which was evidenced by immunofluorescence analysis. No treatment‐related adverse events were documented. Taken together, targeting type 2 inflammation with dupilumab may be an effective and safe treatment option for EBP.
As a next-generation high-power lighting technology, laser lighting has attracted great attention in high-luminance applications. However, thermally robust and highly efficient color converters ...suitable for high-quality laser lighting are scarce. Despite its versatility, the phosphor-in-glass (PiG) has been seldom applied in laser lighting because of its low thermal conductivity. In this work, we develop a unique architecture in which a phosphor-in-glass (PiG) film was directly sintered on a high thermally conductive sapphire substrate coated by one-dimensional photonic crystals. The designed color converter with the composite architecture exhibits a high internal quantum efficiency close to that of the original phosphor powders and an excellent packaging efficiency up to 90%. Furthermore, the PiG film can even be survived under the 11.2 W mm–2 blue laser excitation. Combining blue laser diodes with the YAG-PiG-on-sapphire plate, a uniform white light with a high luminance of 845 Mcd m–2(luminous flux: 1839 lm), luminous efficacy of 210 lm W–1, and correlated color temperature of 6504 K was obtained. A high color rendering index of 74 was attained by adding a robust orange or red phosphor layer to the architecture. These outstanding properties meet the standards of vehicle regulations, enabling the PiG films with the composite architecture to be applied in automotive lighting or other high-power and high-luminance laser lighting.
